Cyber Hymnal: Even though the website looks like it hasn’t been touched since 1995, there are a massive number of hymn stories for well known and obscure hymns. This site also has many forgotten verses omitted by hymnal editors who limit any hymn to four verses.

Hymnology

Hymnology books tend to involve more rigorous academic research. Often they’re more focused on an era or on a broad overview than on individual hymn stories. Some are easier reading than others.

A Dictionary of Hymnology, 2 volumes, John Julian: This 1957 book is the authority in the field. It’s not that it has zero mistakes, but it was certainly far and away the most accurate up to that point and to this day most of it still holds up fairly well.